<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //统计字符串中每个字符的个数？以对象的形式返回
       
   
        // 结果
        // { a:5， b: 出现次数, ...}

        var str = 'abcdacbabcbababcbabcabd'
        var arr = str.split('')
        var obj = arr.reduce(function(pre,cur){
            if(cur in pre){
                pre[cur] += 1
            }else{
                pre[cur] = 1
            }
            return pre
        },{})
        // console.log(obj);
        for(var key in obj){
             console.log(key + '出现了' + obj[key] +'次')
        }
        
    </script>
</body>
</html>